Highly efficient multiple reflection photosensitive optoelectronic device with optical concentrator

ABSTRACT

Highly efficient photon recycling photosensitive optoelectronic device (POD) structures are disclosed which may include optical concentrating non-imaging collectors. Such device structures may be utilized with both organic and inorganic photoconverting heterostructures to enhance photoconversion efficiency. These photo recycling POD structures are particularly well suited for use with organic photoactive materials.

FIELD OF INVENTION

The present invention generally relates to thin-film photosensitiveoptoelectronic devices. More specifically, it is directed tophotosensitive optoelectronic devices, e.g., solar cells, withstructural designs to enhance photoconversion efficiency by optimizingoptical geometry for use with optical concentrators.

BACKGROUND OF THE INVENTION

Optoelectronic devices rely on the optical and electronic properties ofmaterials to either produce or detect electromagnetic radiationelectronically or to generate electricity from ambient electromagneticradiation. Photosensitive optoelectronic devices convert electromagneticradiation into electricity. Solar cells, also known as photovoltaic (PV)devices, are specifically used to generate electrical power. PV devicesare used to drive power consuming loads to provide, for example,lighting, heating, or to operate electronic equipment such as computersor remote monitoring or communications equipment. These power generationapplications also often involve the charging of batteries or otherenergy storage devices so that equipment operation may continue whendirect illumination from the sun or other ambient light sources is notavailable.

The falloff in intensity of an incident flux of electromagneticradiation through a homogenous absorbing medium is generally given by:

 I=I ₀ e ^(−ax)  (1)

where I₀ is the intensity at an initial position, α is the absorptionconstant and x is the penetration depth. Thus, the intensity decreasesexponentially as the flux progresses through the medium. Accordingly,more light is absorbed with a greater thickness of absorbent media or ifthe absorption constant can be increased. Generally, the absorptionconstant for a given photoconductive medium is not adjustable. Forcertain photoconductive materials, e.g.,3,4,9,10-perylenetetracarboxylic-bis-benzimidazole (PTCBI), or copperphthalocyanine (CuPc), very thick layers are undesirable due to highbulk resistivities. However, by suitably re-reflecting, or recycling,light several times through a given thin film of photoconductivematerial the optical path through a given photoconductive material canbe substantially increased without incurring substantial additional bulkresistance. However, a solution is needed which efficiently permitselectromagnetic flux to be collected and delivered to the cavitycontaining the photoconductive material while also confining thedelivered flux to the cavity so that it can absorbed.

Less expensive and more efficient devices for photogeneration of powerhave been sought to make solar power competitive with presently cheaperfossil fuels. Therefore organic photoconductors, such as CuPc and PTCBI,have been sought as materials for organic photosensitive optoelectronicdevices (OPODs) due to potential cost savings. The high bulkresistivities noted above make it desirable to utilize relatively thinfilms of these materials. However, the use of very thin organicphotosensitive layers presents other obstacles to production of anefficient device. As explained above, very thin photosensitive layersabsorb a small fraction of incident radiation thus keeping down externalquantum efficiency. Another problem is that very thin films are moresubject to defects such as shorts from incursion of the electrodematerial. Co-pending U.S. patent application Ser. No. 09/449,801entitled “Organic Photosensitive Optoelectronic Device With an ExcitonBlocking Layer” (hereinafter “'801 Application”) incorporated herein byreference describes photosensitive heterostructures incorporating one ormore exciton blocking layers which address some of the problems withvery thin film OPODs. However, other solutions are needed to address theproblem of low photoabsorption by very thin films, whether the films areorganic or inorganic photoconductors.

It has been known to use optical concentrators, as known as Winstoncollectors, in the fields of solar energy and radiation detection. Suchconcentrators have been used primarily in thermal solar collectiondevices wherein a high thermal gradient is desired. To a lesser extent,they have been used with photovoltaic solar conversion devices. However,it is thought that such applications have been directed to deviceswherein photoabsorption was expected to occur upon initial incidence oflight upon the active photoconductive medium. If very thinphotoconductor layers are used, it is likely that much of theconcentrated radiation will not be absorbed. It may be reflected backinto the device environment, absorbed by the substrate or merely passthrough if the substrate is transparent Thus, the use of concentratorsalone does not address the problem of low photoabsorption by thinphotoconductive layers.

Optical concentrators for radiation detection have also been used forthe detection of {haeck over (C)}erenkov or other radiation withphotomultiplier (“PM”) tubes. PM tubes operate on an entirely differentprinciple, i.e., the photoelectric effect, from solid state detectorssuch as the OPODs of the present invention. In a PM tube, lowphotoabsorption in the photoabsorbing medium, i.e., a metallicelectrode, is not a concern, but PM tubes require high operatingvoltages unlike the OPODs disclosed herein.

The cross-sectional profile of an exemplary non-imaging concentrator isdepicted in FIG. 1. This cross-section applies to both a conicalconcentrator, such as a truncated paraboloid, and a trough-shapedconcentrator. With respect to the conical shape, the device collectsradiation entering the circular entrance opening of diameter d₁ within±θ_(max) (the half angle of acceptance) and directs the radiation to thesmaller exit opening of diameter d₂ with negligible losses and canapproach the so-called thermodynamic limit. This limit is the maximumpermissible concentration for a given angular field of view. Atrough-shaped concentrator having the cross-section of FIG. 1 alignedwith its y axis in the east-west direction has an acceptance field ofview well suited to solar motion and achieves moderate concentrationwith no diurnal tracking. Vertical reflecting walls at the trough endscan effectively recover shading and end losses. Conical concentratorsprovide higher concentration ratios than trough-shaped concentrators butrequire diurnal solar tracking due to the smaller acceptance angle.(After High Collection Nonimaging Optics by W. T. Welford and R.Winston, (hereinafter “Welford and Winston”) pp 172-175, Academic Press,1989, incorporated herein by reference).

SUMMARY AND OBJECTS OF INVENTION

The present invention discloses photosensitive optoelectronic devicestructures which trap admitted light and recycle it through thecontained photosensitive materials to maximize photoabsorption. Thedevice structures are particularly suited for use in combination withoptical concentrators.

It is an object of this invention to provide a high efficiencyphotoconversion structure for trapping and converting incident light toelectrical energy.

It is a further object to provide a high efficiency photoconversionstructure incorporating an optical concentrator to increase thecollection of light.

It is a further object to provide a high efficiency photoconversionstructure in which the incident light is admitted generallyperpendicular to the planes of the photosensitive material layers.

It is a further object to provide a high efficiency photoconversionstructure in which the incident light is admitted generally parallel tothe planes of the photosensitive material layers.

It is a further object to provide a high efficiency photoconversionstructure utilizing generally conical parabolic optical concentrators.

It is a further to provide a high efficiency photoconversion structureutilizing generally trough-shaped parabolic optical concentrators.

It is a further object to provide a high efficiency photoconversionstructure having an array of optical concentrators and waveguidestructures with interior and exterior surfaces of the concentratorsserving to concentrate then recycle captured radiation.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present invention will be morereadily apparent from the following detailed description of exemplaryembodiments taken in conjunction with the attached drawings.

FIG. 1 is a cross-sectional profile of a prior art radiationconcentrator for use in conjunction with the present invention.

FIGS. 2A-2E depict embodiments of device structures in accord with thepresent invention in which light is accepted in a direction generallyperpendicular to the planes of the photosensitive layers.

FIG. 2A is side view of a perpendicular type embodiment with aconcentrator attached.

FIG. 2B is top down view of FIG. 2A along line A—A having a circularaperture for use with a conical concentrator.

FIG. 2C is a top down view of FIG. 2A along line A—A having arectangular aperture for use with a trough-shaped concentrator.

FIG. 2D is a perspective representation of a collection of perpendiculartype PODs with conical concentrators.

FIG. 2E is a perspective representation of a collection of perpendiculartype PODs with trough-shaped concentrators.

FIG. 3 is a cross-sectional view of a portion of an array ofperpendicular type PODs with concentrators wherein the concentratorsreflect light on their interior and exterior surfaces.

FIGS. 4A-4E depict embodiments of device structures in accord with thepresent invention in which light is accepted in a direction generallyparallel to the planes of the photosensitive layers.

FIG. 4A is side view of a parallel type embodiment with a concentratorattached.

FIG. 4B is end-on view of FIG. 4A along line B—B having a circularaperture for use with a conical concentrator.

FIG. 4C is a end-on view of FIG. 4A along line B—B having a rectangularaperture for use with a trough-shaped concentrator.

FIG. 4D is a perspective representation of a parallel type POD with aconical concentrator.

FIG. 4E is a perspective representation of a parallel type POD with atrough-shaped concentrator.

DETAILED DESCRIPTION

In FIG. 2A, a cross-sectional view which can correspond to two differentdevice structures is depicted. Both structures permit light to beintroduced into a reflective cavity, or waveguide, containingphotosensitive layers such that the light is initially incident in adirection generally perpendicular to the planes of the photosensitivelayers so this type of structure is generally referred to herein as a“perpendicular type structure”. A perpendicular type structure can havetwo types of preferably parabolic cross-section concentrators asdescribed above—“conical” and “trough-shaped”—FIGS. 2B-2E providedifferent views on conical versus trough-shaped structures whose commoncross-section is shown in FIG. 2A. The same numerals are used forcorresponding structure in each of FIGS. 2A-2E.

Accordingly, light incident from the top of these embodiments entersinto one or more concentrator structures 2B01 (conical) or 2C01(trough-shaped). The light admitted to each concentrator is thenreflected into an aperture 2B02 or 2C02 in top reflective layer 203. Asshown in FIGS. 2B and 2C, aperture 2B02 is a generally circular shapedopening for use with a conical concentrator, and aperture 2C02 is agenerally rectangular shaped opening for use with a trough-shapedconcentrator. Only the bottom surface of layer 203 need be reflective sothe top surface may be non-reflective and/or be optionally coated with,for example, a protective layer to enhance weather resistance.Passivated oxides or polymer coatings, for example, may be suitableprotective coatings. After passing through the aperture, the admittedradiation is trapped in a waveguide structure formed between top layer203 and bottom reflective layer 204. The space between the two layers isoccupied by several layers comprising one of the inorganicphotosensitive optoelectronic devices known in the art made, forexample, from silicon, or one of the organic photosensitiveoptoelectronic devices (“OPODS”) such as those disclosed in co-pendingU.S. patent application Ser. Nos. 09/136,342, 09/136,166, 09/136,377,09/136,165, 09/136,164 to Forrest et al. (the “Forrest Applications”),which are herein incorporated by reference in their entirety or in the'801 Application.

More specifically, in an exemplary embodiment of an OPOD with an opticalconcentrator geometry, and with reference particularly to FIG. 2A, belowtop layer 203 is a transparent, insulating layer 205 of, for example,glass or plastic, through which the light admitted by aperture 2B02 or2C02 initially traverses. On its initial pass, the light then traversesa transparent electrode 206 of, for example, degenerately doped ITO. Onits initial pass, the light then traverses one or more active layers 207which may include one or more rectifying junctions, or exciton blockinglayers for efficient conversion of optical energy to electrical energy.An exciton blocking layer can comprise2,9-dimethyl4,7-diphenyl-1,10-phenanthroline (BCP), as disclosed in the'801 Application. Any light which is not absorbed on this pass isreflected by layer 204 back through active layers 207, transparentelectrode 206, and transparent insulating layer 205 to be reflected offof top layer 203 to repeat the cycle again until the light is completelyabsorbed. Layer 204 is typically a metallic film such as silver oraluminum which also can serve as the lower electrode. Alternatively, thelower electrode could be in whole or part a transparent conductivematerial such as degenerately doped ITO in conjunction with a reflectivemetallic film which in turn could optionally be deposited upon asubstrate such as glass, metal or plastic. FIG. 2A depicts two typicalincident light rays. Those of ordinary skill in the art will appreciatethat there are numerous other possible trajectories for incidentradiation and that the ray depicted is merely for illustration.

The process of trapping the admitted light until it is absorbed enhancesthe efficiency of the photoconversion and may be referred to as “opticalrecycling” or “photon recycling”. A structure designed to trap lightwithin may generally be called a waveguide structure, or also an opticalcavity or reflective cavity. The optical recycling possible within suchoptical cavities or waveguide structures is particularly advantageous indevices utilizing relatively high resistance organic photosensitivematerials since much thinner photoactive layers may be used withoutsacrificing conversion efficiency.

In FIGS. 2D and 2E, a certain number of PODs with concentrators areshown in one integrated structure. Those of ordinary skill in the artwould appreciate that the number of PODs in such integrated structuresmay be increased as desired. In FIG. 2E it should be appreciated thatthe trough-shaped concentrator are shown having open ends. Optionally,the ends of a trough are closed with a structure having a reflectingsurface facing the interior of the trough to help capture additionallight into the apertures. Vertical or sloped planar surfaces may beused. Also, each end of the trough may be closed with a shape generallyresembling half of a parabolic cone. Such structures permit the troughinterior surface to be smoothly curved in its full extent.

It should be appreciated in the array of perpendicular-type PODsdepicted in FIGS. 2D and 2E with reference to FIG. 2A, that after theadmitted light has entered an aperture 2B02 or 2C02, the light will notbe reflected back across the plane defined by the top surface of the topreflective layer 203. Therefore, the space between the exterior of theconcentrator and top layer 203 may be empty or filled with anon-transparent material. For mechanical stability, it is preferablethat at least part of this volume should be filled with material toprovide support for the concentrator. Also, it should be appreciatedthat the FIG. 2A, 2D, 2E structures as described above utilize threeseparate reflective surfaces for, respectively, the interior of theconcentrator, the upper reflective surface of the waveguide structureand the lower reflective surface of the waveguide structure. In FIG. 3,an alternative array structure is depicted in cross-section which canutilize a single reflective film to provide both the concentratorreflections and the “upper” waveguide reflections. Theconcentrator/reflector 301 is a reflective layer, typically metal suchas silver or aluminum, deposited on a layer 302 of molded or casttransparent insulating material such as plastic or glass. Layer 302 ismade with the shape of the concentrator array formed into it. Thetransparent upper electrode, one or more photosensitive layers, labeledcollectively as 303, and lower reflective layer (optionally also thelower electrode) 304 complete the waveguide structure. This arrangementallows the manufacture of a POD concentrator array to begin with apreformed bare concentrator array structure. Thereafter, a double-dutyreflective coating can be deposited on the concentrator side of thearray structure and the photoactive and conductive layers for extractionof photogenerated current can all be deposited on the lower surfaceusing masking and photolithographic techniques. Since physical supportis provided by layer 302, reflective layer 301 can be made much thinnerthan would be possible if layer 301 were needed to be a partly orcompletely self-supporting concentrator/reflector.

It should be appreciated that as just described, layer 301 hasreflecting surfaces on both its interior and exterior parabolicsurfaces. Optionally, layer 301 could be two separate coatings on theinterior and exterior of a generally conical or trough-shaped basematerial such as molded or cast plastic or glass. This implementationmore easily permits the concentrator interior and exterior surfaceshapes to be slightly different thus permitting independent optimizationof the concentrator reflections and the waveguide structure reflections.

In FIGS. 4A-4E, different versions of structures which permit light tobe introduced into a reflective cavity, or waveguide, containingphotosensitive layers such that the light is initially incident in adirection generally parallel to the planes of the photosensitive layersso that this type of structure is generally referred to herein as a“parallel type structure”. As with perpendicular type structures,parallel type structures can have both generally “conical” and“trough-shaped” type concentrators. FIGS. 4B-4E provide different viewson conical versus trough-shaped structures whose common cross-section isshown in FIG. 4A. The same numerals are used for corresponding structurein each of FIGS. 4A-4E.

Accordingly, light incident from the top of these embodiments entersinto one or more concentrator structures 4B01 (conical) or 4C01(trough-shaped). The light admitted to each concentrator is reflectedinto an aperture 4B02 or 4C02 at the base of each concentrator. As shownin FIGS. 4B and 4C, aperture 4B02 is a generally circular shaped openingfor use with a generally conical concentrator, and aperture 4C02 is agenerally rectangular shaped opening for use with a trough-shapedconcentrator. The remaining structure is now described with respect to atypical incident light ray but those of ordinary skill in the art willappreciate that there are numerous other possible trajectories forincident radiation and that the ray depicted is merely for illustration.The typical ray enters a transparent, insulating layer 403 of, forexample, glass or plastic. The typical ray then reflects off reflectivelayer 404, which is typically a metallic film of, for example, silver oraluminum. The reflected ray then retraverses part of transparent layer403 and then traverses transparent conductive layer 405 which serves asone electrode of the device and is typically a conductive oxide such asdegenerately doped ITO. The typical ray then traverses the photoactivelayers 406 which are photosensitive rectifying structures such as thosedescribed in the Forrest Applications or the '801 Application orinorganic photosensitive optoelectronic structures made from, forexample, silicon. Any optical intensity in the typical ray that has notbeen absorbed reflects off upper reflective layer 407 which may be ametallic reflective film of, for example, silver or aluminum andtypically serves as an electrode layer. Optionally, the electrodefunction may be served in part or whole by a second transparentelectrode with the reflective function provided by a separate layer.

In attaching the concentrator structure to the POD, care should be takento avoid shorting of the electronically active layers. This can beaccomplished by providing a thin insulating protective coating aroundthe edges of the photoconductive layers. It should be furtherappreciated that a reflective coating may be optionally located aroundthe edges of the device to reflect light back into the device. Morespecifically, in FIG. 4A, a reflective layer (not shown) electricallyinsulated from the electronically active layers would optionally beplaced at the right end of FIG. 4A so that (as illustrated) the typicalray could reflect back toward the concentrator. It should be appreciatedthat the proportions of the device depicted in the figures are merelyillustrative. The device may be made generally thinner vertically andlonger horizontally with the result that most light is absorbed beforeit ever reaches the edges of the device opposed to the concentrator.Only light which is truly normal to the plane of the aperture and thustruly parallel to the planes of the photoactive layers would have asubstantial probability of reaching the edge opposite the concentrator.This should represent a small fraction of the incident light.

In FIG. 4B, aperture 4B02 is illustrated as covering a section of onlytransparent insulating layer 403. Provided the instructions aboverelating to preventing electrical shorts between electrically activelayers is heeded, the concentrator 4B01 and aperture 4B02 may bedisposed to allow direct illumination of transparent electrode 405 orphotoactive layers 406. In FIG. 4C, it should be appreciated thattransparent insulating layer 403 is not depicted since generallyrectangular aperture 4C02 is shown as completely overlapping layer 403in the view shown. As with aperture 4B02, aperture 4C02 may be varied insize along with concentrator 4C01 to provide direct illumination of moreor less of the interior of the POD.

FIGS. 4D and 4E are perspective illustrations of exemplary embodimentsof the present invention in parallel type structures. In FIG. 4D, agenerally conical concentrator is illustrated delivering incident lightto a parallel type structure having an upper reflective layer 408, oneor more photosensitive layers and rectifying structures including one ormore transparent electrodes labeled collectively as 409, and atransparent insulating layer and bottom reflective layer labeledcollectively as 410. FIG. 4E depicts a generally trough-shapedconcentrator 4C01 delivering light to a similar POD structure in whichthe layers are labeled accordingly. It should be appreciated that thetrough-shaped concentrator is shown having open ends which mayoptionally be closed off with a reflecting surface as described abovewith regard to FIG. 2E.

The concentrator may be formed of only metal or of molded or cast glassor plastic which is then coated with a thin metallic film. With theparallel type structure, the waveguide photoabsorbing structures aremore readily manufactured separately from the concentrator structureswith the pieces being attached subsequently with suitable adhesivebonding materials. An advantage of the perpendicular type structure, asdescribed above, is that its manufacture can begin with preformedconcentrator structures which are used as the substrate for furtherbuild up of the device.

It should be appreciated that the terms “conical” and “trough-shaped”are generally descriptive but are meant to embrace a number of possiblestructures. “Conical” is not meant to be limiting to an shape having avertical axis of symmetry and whose vertical cross-section would haveonly straight lines. Rather, as described above with reference toWelford and Winston, “conical” is meant to embrace, among other things,a structure having a vertical axis of symmetry and a generally parabolicvertical cross section as depicted in FIG. 1. Further, the presentinvention is not limited to concentrators, either “conical” or“trough-shaped”, having only smoothly curved surfaces. Rather, thegeneral conical or trough shape may be approximated by some number ofplanar facets which serve to direct incident light to the exit aperture.

Further, the generally circular and generally rectangular apertures arepreferred for use with optical concentrators but are exemplary. Othershapes for apertures are possible particularly in the perpendicular typestructure. Concentrators having generally parabolic sloped sides may befitted to a number of aperture shapes. However, the 3D parabolic andtrough-shaped concentrator with their respective circular andrectangular apertures are preferred.

It should also be appreciated that the transparent insulating layer,e.g., 205 or 403, is present to prevent optical microcavity interferenceeffects. Therefore, the layer should be longer than the opticalcoherence length of the incident light in all dimensions. Also, thetransparent insulating layer can be placed on either side of thephotoactive layers. For example, in FIG. 2A, the aperture could be inlayer 204 and layer 203 could be just a reflecting layer. Accordingly,any concentrator 2B02 or 2C02 would be placed over the aperture whereverit may lie. This would have the effect of permitting the admitted lightto reach the photoactive layers initially before reaching thetransparent insulating layer. For many possible photoactive materials,however, the embodiments specifically disclosed herein, e.g., FIG. 2A,are preferred since they allow the transparent insulating layer toprotect the underlying photoactive layers from the environment. Exposureto atmospheric moisture and oxygen may be detrimental to certainmaterials. Nonetheless, those of ordinary skill in the art wouldunderstand this alternate version of the device with the benefit of thisdisclosure.

While the particular examples disclosed herein refer preferably toorganic photosensitive heterostructures the waveguide and waveguide withconcentrator device geometries described herein suitable as well forother photosensitive heterostructures such as those using inorganicmaterials and both crystalline and noncrystalline photosensitivematerials. The term “photosensitive heterostructure” refers herein toany device structure of one or more photosensitive materials whichserves to convert optical energy into electrical energy whether suchconversion is done with a net production or net consumption ofelectrical energy. Preferably organic heterostructures such as thosedescribed in the Forrest Applications are used.

Also, where a reflective electrode layer is called for herein, suchelectrode could also be a composite electrode comprised of a metalliclayer with an transparent conductive oxide layer, for example, an ITOlayer with a Mg:Ag layer. These are described further in the ForrestApplications.

It should be appreciated that the terms “opening” and “aperture” aregenerally synonymous and may be used herein somewhat interchangeably torefer to the entrance or exit of a concentrator as well as a transparenthole or window which allows radiation to reach the interior of a POD.Where it is necessary to draw a distinction between the two types ofopenings or apertures, for example, in the claims, antecedent contextwill provide the suitable distinction.

Thus, there has been described and illustrated herein waveguidestructures for PODs and use particularly in conjunction with opticalconcentrators. Those skilled in the art, however, will recognize thatmany modifications and variations besides those specifically mentionedmay be made in the apparatus and techniques described herein withoutdeparting substantially from the concept of the present invention.Accordingly, it should be clearly understood that the form of thepresent invention as described herein is exemplary only and is notintended as a limitation on the scope of the present invention.

We claim:
 1. A photosensitive optoelectronic device comprising: a firstreflective layer; a transparent insulating layer adjacent the firstreflective layer; a transparent first electrode layer adjacent thetransparent insulating layer; a photosensitive heterostructure adjacentthe transparent electrode; and a second electrode and reflective layersubstantially parallel to the first reflective layer and adjacent thephotosensitive heterostructure in spaced opposition to the firstelectrode, wherein one of the first reflective layer or the secondelectrode and reflective layer has an aperture for admittance of opticalradiation to the photosensitive heterostructure.
 2. The device of claim1 wherein the aperture has a substantially circular shape.
 3. The deviceof claim 1 wherein the aperture has a substantially polygonal shape. 4.The device of claim 3 wherein the aperture has a substantiallyrectangular shape.
 5. The device of claim 1 further comprising anoptical concentrator having an entrance opening and an exit openingwherein the exit opening is attached to the aperture.
 6. The device ofclaim 5 wherein the optical concentrator has substantially parabolicallysloped sides between the entrance opening and the exit opening.
 7. Thedevice of claim 5 wherein the optical concentrator has a substantiallyconical shape between the entrance opening and the exit opening.
 8. Thedevice of claim 6 wherein the optical concentrator has the shape of atruncated paraboloid.
 9. The device of claim 5 wherein the opticalconcentrator is substantially trough-shaped.
 10. The device of claim 5wherein the optical concentrator has an inner surface comprising aplurality of planar regions collectively approximating a conical shape.11. The device of claim 5 wherein the optical concentrator has an innersurface comprising a plurality of planar regions collectivelyapproximating a trough shape.
 12. The device of claim 1 wherein thephotosensitive heterostructure comprises organic materials.
 13. Thedevice of claim 12 further comprising an exciton blocking layer disposedadjacent one of the first electrode layer and the second electrode andreflective layer.
 14. The device of claim 12 wherein the photosensitiveheterostructure comprises a hole transporting layer adjacent to anelectron transporting layer.
 15. The device of claim 14 wherein the holetransporting layer comprises CuPc and the electron transporting layercomprises PTCBI.
 16. The device of claim 15 further comprising anexciton blocking layer disposed between the electron transporting layerand one of the first electrode layer and the second electrode andreflective layer, wherein the second electrode and reflective layer is acathode.
 17. The device of claim 16 wherein the exciton blocking layercomprises 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline.
 18. The deviceof claim 1 wherein the photosensitive heterostructure is a stackedorganic photosensitive optoelectronic device.
 19. The device of claim 1wherein the photosensitive heterostructure comprises inorganicphotosensitive materials.
 20. The device of claim 1 wherein thephotosensitive heterostructure is a silicon based photovoltaicstructure.
 21. A photosensitive optoelectronic device comprising: asubstantially planar first reflective layer; a transparent insulatinglayer adjacent the first reflective layer; a transparent first electrodelayer adjacent the transparent insulating layer; a photosensitiveheterostructure adjacent the transparent electrode; and a substantiallyplanar second electrode and reflective layer substantially parallel tothe first reflective layer and adjacent the photosensitiveheterostructure in spaced opposition to the first electrode layer,wherein the device has an exterior face transverse to the planes of thereflective layers, the exterior face having an aperture for admission ofincident radiation to the interior of the device.
 22. The device ofclaim 21 wherein the aperture has a substantially circular shape. 23.The device of claim 21 wherein the aperture has a substantiallypolygonal shape.
 24. The device of claim 21 wherein the aperture has asubstantially rectangular shape.
 25. The device of claim 21 furthercomprising an optical concentrator having an entrance opening and anexit opening wherein the exit opening is attached to the aperture. 26.The device of claim 25 wherein the optical concentrator hassubstantially parabolically sloped sides between the entrance openingand the exit opening.
 27. The device of claim 25 wherein the opticalconcentrator has a substantially conical shape between the entranceopening and the exit opening.
 28. The device of claim 27 wherein theoptical concentrator has the shape of a truncated paraboloid.
 29. Thedevice of claim 25 wherein the optical concentrator is substantiallytrough-shaped.
 30. The device of claim 25 wherein the opticalconcentrator has an inner surface comprising a plurality of planarregions collectively approximating a conical shape.
 31. The device ofclaim 25 wherein the optical concentrator has an inner surfacecomprising a plurality of planar regions collectively approximating atrough shape.
 32. The device of claim 21 wherein the photosensitiveheterostructure comprises organic materials.
 33. The device of claim 32further comprising an exciton blocking layer disposed adjacent one ofthe first electrode layer and the second electrode and reflective layer.34. The device of claim 33 wherein the photosensitive heterostructurecomprises a hole transporting layer adjacent to an electron transportinglayer.
 35. The device of claim 34 wherein the hole transporting layercomprises CuPc and the electron transporting layer comprises PTCBI. 36.The device of claim 35 further comprising an exciton blocking layerdisposed between the electron transporting layer and one of the firstelectrode layer and the second electrode and reflective layer, whereinthe second electrode and reflective layer is a cathode.
 37. The deviceof claim 36 wherein the exciton blocking layer comprises2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline.
 38. The device of claim21 wherein the photosensitive heterostructure is a stacked organicphotosensitive optoelectronic device.
 39. The device of claim 21 whereinthe photosensitive heterostructure comprises inorganic photosensitivematerials.
 40. The device of claim 21 wherein the photosensitiveheterostructure is a silicon based photovoltaic structure.
 41. Aphotosensitive optoelectronic device comprising an array ofphotosensitive optoelectronic waveguide structures and opticalconcentrators, each optical concentrator having an entrance aperture andan exit aperture, the array having: a first reflective surface formed bythe interior surfaces of the concentrators; a second reflective surfaceformed by the exterior surfaces of the concentrators; a transparentinsulating layer, the transparent insulating layer having a non-planarupper surface in contact with the second reflective surface and asubstantially planar lower surface; a transparent first electrode layerin contact with the lower surface of the transparent insulating layer; aphotosensitive heterostructure in contact with the transparentelectrode; and a third reflective surface in contact with thephotosensitive heterostructure, the third reflective surface being thesurface of a reflective second electrode layer, wherein the concentratorinterior surfaces and the concentrator exterior surfaces aresubstantially parabolically sloped so that incident radiation isdirected through the concentrator exit apertures and reflected betweenthe second reflective surface and the third reflective surface until theradiation is substantially photoconverted by the photosensitiveheterostructure.